It was fun to see this action, and consequent no written violation, but it should be considered an exception IMV. Got a "where in the heck is a cop' story to that regard:
New York State a few weeks back, running the usual 1 MPH under the posted and cars are lining up behind me, 5 deep. Pick up truck coming down entry ramp, so we do the usual left signal, check mirror's, slight acceleration, and switch to left lane for merge allowance. Check right mirror, signal right, and check mirrors again before slipping back over into the right lane. Pick up truck is now passing me on the right.
He had to see my blinker on.
He passes and we resume our lead spot in the right lane. Turns out, the car second behind me all the while was a NY Highway Patrol vehicle (and the probable reason cars were lining up behind me) Ahhhh....the unmistakable sound of a kicked downed 8 cylinder as he/she passes me and is closing fast on the PU truck, who has pulled away from the train, in short order. Myself and the car behind had allowed for the merge, with the Leo sagging back to allow the PU to move in ahead of him/her.
Leo knows had I not checked the mirror again before moving back over, it would likely have been an accident involving at least 3 cars. Flip side of the OP post? It was nice to see someone on the spot, and a ticket given for stupid moves made every day. Actually smiled as I drove by the blinking lights.